Coordinate graphing is a way to present information as a picture. By
drawing a grid and assigning values to each spot on the grid, the relationships
can be shown as points and lines.

The grid, or graph is made up of two axis, an X axis that runs across
the bottom and a Y axis that runs up and down. Each axis is numbered,
usually starting at zero. This is what a coordinate graph (with one
labeled point) looks like:

What are coordinate graphs used for?

These graphs are used as a visual aid, usually to show a relationship
between whatever X is and whatever Y is. When we deal with numbers alone,
sometimes we miss patterns. By putting the information on a coordinate
graph, the picture is clearer. Graphs like these appear as descriptions
or trends over time, like how an investment has increased or decreased,
or the growth of plants with different fertilizers.

Any time two things can be related (so that a change in one means a
change in the other) a coordinate graph can draw a helpful picture of
what's happening.

A basic problem in coordinate graphing.

A gardener wants to know how much plant food to use on her tomatoes.
She tries different amounts and measures how many pounds of tomatoes
she gets with each amount of fertilizer. After gathering all these numbers,
she puts the information on a coordinate graph to see if there is a
pattern.

Her graph looks like this:

She puts a point on the graph for each time she changes
the amount of fertilizer (X) and how many pounds of tomatoes she gets
(Y). Finally, in the second coordinate graph, she draws lines connecting
the points. This final picture makes it obvious that she gets more
tomatoes when she uses more fertilizer, but only up to a point - where
the line is highest. Adding more fertilizer after that actually lowers
the amount of tomatoes.

Who first used this form of math?

RenÉ Descartes (pronounced day-kart) is credited
with developing the Cartesian coordinate system, another name for
coordinate graphing. Descartes was an amazing genius who lived in
the 17th century. Besides being a mathematician, he was also a philosopher,
a scientist and a writer. You may already know one of his quotes:
I think, therefore I am.

An interesting fact about coordinate
graphing:

The GPS (Global Positioning System) that we find in cars is based on
coordinate graphing. If an imaginary grid is drawn around the entire
earth, each point (or location) on the earth can then be expressed as
an X and Y coordinate. With GPS, these are called latitude and longitude,
but the idea is exactly the same.

By knowing where you are on this global grid, the distance and direction
to anywhere else can be calculated. This is how GPS figures out what
to tell you.